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How in-flight Wi-Fi works

28-April-2017 16:45
in Aviation and Travel
by Lawrence Power

We’ve all had the same problem: you walk too far away from your Wi-Fi router and, all of a sudden, your Wi-Fi stops working. We all know that it’s simply because the router’s signal isn’t strong enough to reach you that extra few feet away. There is sadly a limit on the strength of Wi-Fi connectivity. But, if Wi-Fi is so dependent upon your proximity to a router, doesn’t it seem strange that Wi-Fi can work in an aeroplane, 35,000 feet above the ground?

So, how does this technology work? Is the answer routers in the sky? Or an invisible cable dropped down to the ground to keep you connected, as you travel at 900 km/h through the air? Close.

More and more commercial airlines are offering their passengers on-board Wi-Fi, whether free of charge or for an extra add-on fee, and they’re all using one of two ways to do it.

Either, the plane will connect to satellites in geostationary orbit (over 35,000 km above the ground), which send and receive signals to Earth through receivers and transmitters, just as they do to produce television signals and weather forecasts. To do this, the plane must have an antenna on its roof, just like a car, which transmits information to and from your smartphone, and the information is simply passed between the ground and the plane via the satellite. The plane will then have an on-board router that will be used to convert this into Wi-Fi signal for the passengers.

Alternatively, the plane may use ground-based mobile broadband towers to send signals up to the aircraft’s antennas (this time on the base of the plane). The way this works is that, as the plane travels through the air, it will automatically connect to the signals of the nearest tower below its path. The only problem with this is when a plane passes over a large body of water or remote terrain, where there aren’t any broadband towers below, which results in a break in connectivity - just like wandering with your laptop into your garden.

But all of this clever technology doesn’t come cheap (or quickly). The US has the best developed infrastructure of towers and satellite connectivity, so your Wi-Fi on a commercial flight operated by a US company is likely to be cheaper and quicker than on a trip through Europe. The price comes primarily from the antennas which have to be fitted onto the aeroplanes to make the Wi-Fi work. These increase the aeroplane’s drag, which increases fuel costs, without forgetting the added engineering and maintenance costs involved. All of these costs are passed onto the consumer, with Wi-Fi usually being an ‘added’ (costly) extra on today’s flights. What’s more, you might have noticed that, even once you do get yourself connected to the Wi-Fi, it’s often painfully slow. That’s because a satellite connection can only currently offer a speed of up to around 12 Mbps (as opposed to the average U.K household Wi-Fi speed of 28.9 Mbps) and this can be even slower still if everyone on the plane is trying to connect.

But, that being said, technology is moving quickly. The speed and the price of aeroplane Wi-Fi is set to improve as more and more competitors enter the market and innovation truly takes off in this relatively new area of technology. Plus, even 12 Mbps cannot really be complained about at 35,000 feet, now, can it?


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© Chambers of Lawrence Power